• 한국측량학회지
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• 제32권1호
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• pp.9-17
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• 2014

대기의 에너지를 측정하거나 지표면유출을 예측하는 기상 및 수문모델에서 지표면특성(식생피복)을 파악하는 것은 매우 중요한 요소이다. 1978년 Deardorff가 식생피복을 정량적으로 파악하기 위하여 식생피복지수(Vegetation Cover Fraction)를 제안한 후 식생피복지수에 관한 연구가 활발해졌다. 그러나 선행연구에서는 AVHRR, MODIS 그리고 KOMPSAT-2영상과 같은 고 저해상도 위성영상을 이용한 많은 연구가 있었으나, 중해상도 영상인 Landsat에 대한 연구는 미비한 실정이다. 따라서 본 연구는 Landsat OLI영상을 이용하여 식생피복지수 산정방법을 연구하였다. 정확하고 효율적인 식생피복지수 산정방법을 연구하기 위하여, 본 연구에서 제안된 방법과 선행연구방법을 비교평가 하였다. 실험결과 NDVI와 식생피복지수는 많은 연관성을 지니는 것으로 분석되었으며, 본 연구에서 제안된 방법을 이용한 식생피복지수가 특이점을 제외한 RMSE 7.3%로 전체 방법 중에서 가장 높은 정확도를 보였다.

• 대한원격탐사학회지
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• 제26권5호
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• pp.537-547
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• 2010

FPAR는 다양한 육상 생태계 모텔에서 중요한 입력변수로 사용된다. 이 때문에 다양한 global product의 형태로 제공되고 있다. 하지만 한반도를 영역으로 하는 연구에 이를 바로 적용 시 오차가 발생할 수 있고, 이것은 위성자료를 이용한 지면 정보 산출에 있어서 직접적인 오차요인이 된다. 따라서 본 연구에서는 Terra/MODIS와 SPOT/VEGETATION 그리고 ECOCLIMAP 자료를 이용해 한반도에 최적화된 FPAR를 산출 하였고, 또한 기존에 사용하였던 LAI와의 관계식을 사용하지 않고, SPOT/VGT NDVI 로부터 계산된 FVC (Fraction Vegetation Cover)를 직접 이용하여 FPAR를 산출 하였다. 이를 위해 식생지수의 선형/비선형 관계를 이용하여 구하는 경험적인 방법을 적용하여 회귀분석을 수행한 결과 cropland와 forest에서 각각 결정계수 (Coefficient of Determination, $R^2$)가 0.9039. 0.7901으로 정확도가 높은 관계식을 도출해내었다. 최종적으로 Reference FPAR 자료와의 비교 분석을 통해 본 연구에서 산출된 FPAR가 전반적인 패턴을 잘 표현하면서 불규칙하게 발생하던 노이즈 또한 보정된 것을 확인 할 수 있었다. 이렇게 한반도에 최적화된 입력변수의 사용은 산출물의 정확도뿐만 아니라 연구의 질 향상에도 도움을 줄 것으로 사료된다.

• 한국물환경학회지
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• 제28권4호
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• pp.582-594
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• 2012

A simple ecohydorlogic model that simulates hydrologic components and vegetation dynamics simultaneously based on equations of soil water dynamics and vegetation's growth and mortality is discussed. In order to simulate ungauged watersheds, the proposed model is calibrated with indirected estimated observation data set; 1) empirically estimated annual vaporization, 2) monthly surface runoff estimated by NRCS-CN method, and 3) vegetation fraction estimated by SPOT/VEGETATION NDVI. In order to check whether the model is performed well with indirectly estimated data or not, four upper dam watersheds (Andong, Habcheon, Namgang, Milyang) in Nakdong River watershed are selected, and the model is verified.

• 한국방재학회:학술대회논문집
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• 한국방재학회 2008년도 정기총회 및 학술발표대회
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• pp.401-404
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• 2008

The vegetation in the surrounding area of river is a primary factor to increase water level during flood. The influence of vegetation on the river flow in a bank has been investigated by using a hydraulic experiment. For a hydraulic experiment square-shaped piers are used as a model of unsubmerged rigid vegetation in a open channel. For fully developed uniform flows, the water elevation of the experiment was measured as varying the interval of piers and the porosity which presents the fraction of water flowing area in the cross-sectional area. The Manning's roughness coefficient, which implicates energy losses due to the vegetation, was obtained by using the experimental data. As a result, the energy losses were varied when the distance of piers and the porosity of area were changed, and the Manning's coefficient increased nonlinearly when a water elevation increased.

• 한국농공학회논문집
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• 제57권2호
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• pp.67-73
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• 2015

This study evaluated the effects of fibers on the void ratio, compressive strength and repeated freezing and thawing resistance of porous vegetation concrete with binder type (non-sintering inorganic binder and blast furnace slag cement) and natural jute fiber volume fraction (0.0 %, 0.1 % and 0.2 %). The natural jute fiber volume fraction affected the void ratio, compressive strength and repeated freezing and thawing resistance. Added of natural jute fiber resulted in improved properties of the void ratio, compressive strength and freezing and thawing resistance. Also, the both compressive strength and freezing and thawing resistance increased with natural jute fiber volume fraction up to 0.1 % and then decreased with fiber volume fraction at 0.2 %.

• Journal of Biosystems Engineering
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• 제41권2호
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• pp.126-137
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• 2016

Purpose: The overall objective of this study was to evaluate the vegetation fraction of soybeans, grown under different cropping conditions using an unmanned aerial vehicle (UAV) equipped with a red, green, and blue (RGB) camera. Methods: Test plots were prepared based on different cropping treatments, i.e., soybean single-cropping, with and without herbicide application and soybean and barley-cover cropping, with and without herbicide application. The UAV flights were manually controlled using a remote flight controller on the ground, with 2.4 GHz radio frequency communication. For image pre-processing, the acquired images were pre-treated and georeferenced using a fisheye distortion removal function, and ground control points were collected using Google Maps. Tarpaulin panels of different colors were used to calibrate the multi-temporal images by converting the RGB digital number values into the RGB reflectance spectrum, utilizing a linear regression method. Excess Green (ExG) vegetation indices for each of the test plots were compared with the M-statistic method in order to quantitatively evaluate the greenness of soybean fields under different cropping systems. Results: The reflectance calibration methods used in the study showed high coefficients of determination, ranging from 0.8 to 0.9, indicating the feasibility of a linear regression fitting method for monitoring multi-temporal RGB images of soybean fields. As expected, the ExG vegetation indices changed according to different soybean growth stages, showing clear differences among the test plots with different cropping treatments in the early season of < 60 days after sowing (DAS). With the M-statistic method, the test plots under different treatments could be discriminated in the early seasons of <41 DAS, showing a value of M > 1. Conclusion: Therefore, multi-temporal images obtained with an UAV and a RGB camera could be applied for quantifying overall vegetation fractions and crop growth status, and this information could contribute to determine proper treatments for the vegetation fraction.

• 대한원격탐사학회지
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• 제22권3호
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• pp.175-182
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• 2006

Because of the phenological variation of vegetation growth in temperate region, it is often difficult to accurately assess the surface conditions of agricultural croplands, grasslands, and disturbed forests by multi-spectral remote sensor data. In particular, the spectral similarity between soil and dry vegetation has been a primary problem to correctly appraise the surface conditions during the non-growing seasons in temperature region. This study analyzes the spectral characteristics of the mixture of dry vegetation and soil. The reflectance spectra were obtained from laboratory spectroradiometer measurement (GER-2600) and from EO-1 Hyperion image data. The reflectance spectra of several samples having different level of dry vegetation fractions show similar pattern from both lab measurement and hyperspectral image. Red-edge near 700nm and shortwave IR near 2,200nm are more sensitive to the fraction of dry vegetation. The use of hyperspectral data would allow us for better separation between bare soils and other surfaces covered by dry vegetation during the leaf-off season.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2003년도 Proceedings of ACRS 2003 ISRS
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• pp.147-149
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• 2003

The wetness, a function of precipitation and temperature etc, and the warmth, a function of temperature, are the dominant factor for global vegetation distribution. This paper employs the normalized difference vegetation index (NDVI), warmth index (WAI), and wetness index (WEI), and focuses on an essential climate-vegetation relationship at global scale. The NDVI was acquired from ‘Twenty-year global 4-minute AVHRR NDVI dataset.’ The WEI is defined as the fraction of the precipitation to the potential evaporation. The WAI was calculated by accumulating the monthly mean temperature of the portion exceeded 5$^{\circ}C$ throughout the year. Meteorological data for the WEI and WAI calculation were obtained from the ISLSCP CD-ROM. All analyses were conducted for 1 ${\times}$ 1 degree grid box on the terrestrial area of the Earth, and on annual value basis averaged in 1987 and 1988. The result of analyses demonstrated that there are two regimes in their relations, that is, a regime in which NDVIs vary depending on the WEI, and a regime in which NDVIs vary depending on the WAI. These two regimes appeared to correspond to the wetness dominant and warmth dominant vegetation, respectively. The geographical distributions of two regimes were mapped. Most of the world vegetation is categorized into wetness dominant, while warmth dominant vegetation is seen in the high-latitude area mainly to the north of 60$^{\circ}$N in the Northern Hemisphere and high-altitude areas.

• 한국지역지리학회지
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• 제12권4호
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• pp.496-507
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• 2006

본 연구는 고해상도 자료와 하이퍼스펙트럴 자료를 혼용하여 하와이 화산 국립공원 내 해안 지역의 식생을 분류하고자 하였다. 연구지역에 주로 나타나는 식생은 3종의 초본(broomsedge, natal redtop, and pili)과 작은 관목 등으로 대표되는 비초본으로 구분된다. 분류 기법으로는 unsupervised classification과 supervised classification을 결합한 하이브리드법을 이용하여 전체적으로 3단계 분류과정을 적용하였다. 첫째로는, IKONOS 고해상 위성자료를 이용하여, 식생 및 비식생지역을 unsupervised classification법을 통해 분류하였다. 두 번째로는, minimum noise fraction(MNF) transformation을 이용하여 AVIRIS하이퍼스펙트럴 자료로부터 주성분을 추출하여 자료를 압축하는 과정을 거쳤다. 20미터 해상도를 가진 AVIRIS 픽셀들은 대부분 용암면과 식생면으로부터 반사된 복사신호가 혼합되어 있기때문에, 용암과 식생의 지표피복 비율에 따른 선형모형을 적용하여 용암면이 갖는 반사 신호를 각 픽셀로부터 제거하였다. 최종적으로, 각 픽셀에 대하여, 식생피복 비율에 비례하는 AVIRIS 하이퍼스펙트럴 자료의 식생성분을 토대로 maximum likelihood algorithm에 따라 supervised classification법을 적용하여 초지 및 관목으로 대표되는 지표식생을 분류하였다.

• 한국환경과학회지
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• 제9권2호
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• pp.101-108
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• 2000

Through numerical experiment using simplified OSU-1D PBL(Oregon State University One-Dimensional Planetary Boundary Layer) model and field measurement, we studied the impacts of vegetation canopy on heat island that was one of the characteristics of local climaate in urban area. it was found that if the fraction of vegetation was extended by 10 percent, the maximum air temperature and the maximum ground temperature can come down about 0.9${\circ}C$, 2.3${\circ}C$, respectively. Even though the field measurement was done under a little unstable atmospheric condition, the canopy air temperature was lower in the daytime, and higher at night than the air and ground temperature. This result suggests that the extention of vegetation canopy can bring about more pleasant local climate by causing the oasis, the shade and the blanket effect.